Glazed Tunnel in Oceanarium, Barcelona Aquarium

Walk through the acrylic tunnel that runs the length of the Oceanarium, watch sharks swimming closely. The spectacular Oceanarium, which is unique in Europe, is the aquàrium de Barcelona’s largest aquarium and home to the greatest number of species. With a diameter of 36 metres and depth of 5 metres, it contains almost 4 million litres of water. It houses species as diverse as giltheads, moray eels, ocean sunfish, rays and two types of shark: the sand tiger shark (Carcharias taurus) and the sandbar shark (Carcharhinus plumbeus) – the real stars of L’Aquàrium de Barcelona.

A transparent tunnel in excess of 80 metres in length enables you to enjoy a spectacular walk underwater. You can explore the Oceanarium from below and experience the exhilarating feeling of discovering the Mediterranean as if you were walking along the sea floor, just inches away from sharks and other curious species.

The oceanarium is the aquarium’s largest tank (36 meters in diameter and 5 meters deep), and contains 3.7 million liters of salt water. It also has a transparent underwater tunnel over 80 meters long.

The oceanarium shows a synthesis of the most representative species in the Mediterranean, including moray eels, sunfish, bream, rays and the largest sharks in the complex: the bull shark and Milberto’s silky shark. Other interesting species are the marine pig, the great butt and the guitar fish.

Mediterranean aquariums
Mediterranean aquariums has 14 representative aquariums from the different Mediterranean communities with the most characteristic species. In addition, it recreates two protected areas on the Catalan coast: the Ebro Delta and the Medas Islands. Among the recreated spaces are the Posidonia community, the red coral community, the intertidal zone community, the community of caves and crevices, among others.

The Mediterranean Sea, with a length of 3,800 km, maximum width of 800 km, average depth of 1,500 m and points with up to 4,000 m deep is one of the largest marginal seas on the planet. Despite being considered a nutrient-poor sea (oligotrophic), it hosts a diverse range of ecosystems and species. Most notable among them is an important predator: the shark. It is connected to the Atlantic Ocean by the Strait of Gibraltar and the Black Sea by the Bosporus. The small size of its basin and its narrow connection with the Atlantic cause its tides to have very low amplitude (around 25 cm), which gives the sea its unique appearance. The Oceanarium is a microcosm of the Mediterranean Sea.

Other common marine organisms that can be found in the aquarium:
Fauna: Bluntnose sixgill shark (Hexanchus griseus); Atlantic wreckfish (Polyprion americanum); angular roughshark (Oxynotus centrina); common stingray (Dasyatis pastinaca); guitarfish (Rhinobatos rhinobatos); vadigo (Campogramma glaycos); false scad (Caranx rhonchus); leerfish (Lichia amia); pilot fish (Naucrates ductor); mahi-mahi (Coryphaena hippurus); Guinean grunt (Parapristipoma humile); rubber-lip grunt (Plectorhinchus mediterraneus); meagre (Argyrosomus regius); bullet tuna (Auxis rochei); rudderfish (Centrolophus niger); turbot (Psetta maxima); sand tiger shark (Carcharias taurus); sandbar shark (Carcharhinus plumbeus); ocean sunfish (Mola mola).


Shallow rocky coastal community
The shallow rocky ambients near the coast contain a large amount of cracks that serve as a refuge for many organisms. This area is characterised by its highly oxygenated waters and generally warmer than those of the lower layers. We find photophyl vegetation (which needs a lot of light) and green and brown algae. Generally, it is an area with great biological heterogeneity.

The animals in these ambients develop defence mechanisms such as needles associated with poisonous glands, or the adoption of cryptic colours (similar to those of the surroundings). There are also many animals that seek refuge in the cracks and holes in the rocks, such as the moray (Muraena helena).
Among the marine invertebrates that live on the rocks or hidden among them are the sea anemone (Anemonia sulcata), of the well-known jellyfish group. The two have the same defence system: the cnidocysts, cells loaded with stinging liquid that are triggered when touched and penetrate the skin.

Other marine organisms frequently found in this community:
Flora: Cystoseira mediterranea, Coralina elongata
Fauna: Mediterranean moray (Muraena helena), red sea anemone (Actinia equina), brown date mussel (Lithophaga lithophaga), Clathrina clathrus, sea urchin (Arbacia lixula), purple sea urchin (Paracentrotus lividus), violet sea-urchin (Sphaerechinus granularis), white seabream (Diplodus sargus), zebra sea bream (Diplodus cervinus), annular seabream (Diplodus annularis), common two-banded seabream (Diplodus vulgaris), spotted seabass (Dicentrarchus punctatus), peacock wrasse (Symphodus tinca), saupe (Sarpa salpa), kleiner dreiflossen-schleimfisch (Tripterygion melanurus), Tompot blenny (Blennius gattorugine).

Shallow sandy coastal community
Sandy areas, apparently desolated, hide a large number of marine species.

The sandy coastal communities house a poorer fauna and flora that rocky coasts, or at least which are more difficult to observe: Everything is hidden. Sandy areas are the home to a large number of organisms that have adapted their lives to remaining buried in the sand.

Among the fish, we see that the sandy areas are the kingdom of flat fish, rays and spiders. Fish with a toasted colour and pigmented with small white and dark spots (cryptic colouring) that camouflage so well in the sand that they are very difficult to distinguish. Often the only sign of their presence is a light silhouette in the sand, or two small eyes moving nervously, one on either side. Among the invertebrates are the clams that live more numerously alongside sea snails, cuttlefish, sea stars, sea cucumbers and different crustaceans that hide in the sand.

Furthermore, alongside these the marine fanerogamas are beginning to appear (superior plats) that facilitate the settlement of a whole range of associated fauna, both fish and marine invertebrates, which would find it difficult to live without the ideal hiding place and the resources offered by its existence.

Other marine organisms frequently found in this community:
Fauna: Striped red mullet (Mullus surmuletus), Cerianthus membranaceus, warty venus (Venus verrucosa), cottonspinner (Holothuria tubulosa), Astropecten spinulosus, Callionymus festivus, turbot (Psetta maxima), wide-eyed flounder (Bothus podas), common sole (Solea vulgaris), pearly razorfish (Xyrichthis novacula), eagle ray (Myliobatis aquila).

Cave and crevice community
The progressive growth of incrustating algae causes the formation of small cracks between the rocks, thus creating a habitat that is suitable for numerous fish and invertebrates. Generally, water erosion forms a series of tunnels and galleries, which are known as underwater caves, which give very peculiar scenery generally poor in organisms. In these places, the little light there is prevents the growth of vegetable life and as we move inside, the fauna on the walls becomes poorer and poorer until it practically disappears. The same thing happens with other parameters: the oxygen, temperature and nutrients are scarcer on the inside.

In tunnels, on the other hand, thanks to the currents that facilitate water circulation, the walls have a richer fauna, above all filtering invertebrate animals. A similar thing happens with cracks and overhangs. Here, despite not being completely enclosed, the light that reaches them is poor, and as with caves and tunnels they become the favourite habitat or hiding place for a certain number of organisms.

In this way, we can find species that use these places as a refuge, as is the case of the conger eel; others, on the other hand, use them as a favourite habitat to carry out their lives: lobsters. We can also find seasonal fish such as striped red mullet and certain gobies.

Other marine organisms frequently found in this community:

Flora: Lithophyllum expansum, Peyssonnelia rubra.

Fauna: Crambe crambe, Clathrina clathrus, red tubeworm (Serpula vermicularis), slipper lobster (Scyllarus arctus), spiny starfish (Marthasterias glacialis), false coral (Myriapora truncata), sea potato (Halocynthia papillosa), dusky grouper (Epinephelus marginatus), brown meagre (Sciaena umbra), peacock wrasse(Symphodus tinca).

The Neptune Grass community
This plant, Neptune grass (Posidonia oceanica), endemic to the Mediterranean, with tape-like leaves, forms extensive undulating fields that shelter and feed numerous species.

The Neptune grass fields (Posidonia oceanica) are one of the most characteristics communities of the Mediterranean coastline. They spread on gentle beds, preferably of sand in unexposed coastal segments and at depths of between almost the surface and 35 m. This superior plant (it is not an algae) forms beams of 5-7 tape-like leaves of up to almost a metre in length. It grows with such density and extension that it covers the floor, thus forming fields like any land seed used in monocultivation. It is important because it produces a large amount of organic matter (food) and oxygen, (1 m2 leaves provide some 10 l. of oxygen a day). It therefore considerably enriches other ecosystems. It also forms reefs in many bays and beaches that prevent erosion and their disappearance.

This plant serves as a support for other organisms, both algae and animals, especially bryozoans and hydraria that install on its leaves, thus forming the so-called “epiphyte felt”. It also houses a series of fish and invertebrates that feed from its leaves or find sufficient protection to mate and reproduce. Likewise, its sediment enables the development of bivalve molluscs and an infinite number of worms. It is currently in severe regression due to the continuous polluted waste disposal, port constructions, illegal drag fishing, aquiculture, vessel anchoring and the invasion of exotic species.

Other marine organisms frequently found in this community:
Flora: Padina pavonica, Halimeda tuna, Jania rubens.
Fauna: Cliona viridis, Sertularia perpusilla, peacock worm (Sabella pavonina), sea-ears (Haliotis lamellosa), sea hare (Aplysia fasciata), common cuttlefish (Sepia officinalis), cushion star (Asterina gibbosa), purple sea urchin (Paracentrotus lividus), damsel fish (Chromis chromis), short-snouted seahorse (Hippocampus hippocampus), broad-nosed pipefish (Syngnathus typhle), greater pipefish (Syngnathus acus), red star-fish (Echinaster sepositus), saupe(Sarpa salpa).

Shallow algae community
In shallow, calms waters, superior plants and algae form extensive meadows rich in marine life.

This area is characterised as being calmer and having less light than the surface waters. The progressive attenuation of the light causes a change in the vegetation and general scenery. The vegetable species of algae and marine plants adapted to conditions of little light, esciaphyls,replace those fully adapted to light, the photophyls. We can find green algae colonising the area thanks to the ryzoids or small roots that keep them fixed to the substrate. The accumulation of their leaves than fall and decompose turn the bed muddy. The fish fauna associated with this vegetable community is around 50 species, including the gobies, striped red mullet, slugs, etc. Occaionally these places are visited by young forms of littoral species in search of refuge.

Other marine organisms frequently found in this community:
Flora: Caulerpa prolifera, lesser Neptune grass (Cymodocea nodosa), Zostera nana.
Fauna: Verongia aerophoba, sea anemone (Actinia cari), Elysia timida, sabellid worm (Spirographis spallanzani), shore clingfish (Lepadogaster lepadogaster), striped red mullet (Mullus surmuletus), Tripterygion melanurus, red-mouthed goby (Gobius cruentatus), damsel fish (Chromis chromis), ornate wrasse (Thalassoma pavo), rainbow wrasse (Coris julis).

Pre-coralline community
When the light falls short, the green plants are progressively replaced by colonies of incrustating animals that form a singular habitat.

The floors that give way to the coralline community are called precoralline. This precoralline community is considered an area of transition and is characterised by its biological richness. When it penetrates through the water, the light is progressively absorbed and rapidly attenuates in the depths. This means that different algae have to occupy the space selectively, establishing different areas of preference according to the intensity and quality of he light that reaches them. The organisms living in these areas have reddish colourings that allow them to camouflage themselves in surroundings where red light does not reach.

Other marine organisms frequently found in this community:
Flora: Purse codium (Codium bursa), Codium vermilara, Cladophora pellucida.
Fauna: Axinella damicornis, boring sponge (Cliona celata), Eunicella singularis, Bonellia viridis, variegated scallop (Chlamys varia), spiny fileclam (Lima lima), european spiny lobster (Palinurus elephas), Antedon mediterranea, european conger (Conger conger), butterfly-blenny (Blennius ocellaris), small red scorpion fish (Scorpaena notata), painted comber (Serranus scriba), comber (Serranus cabrilla), black scorpionfish (Scorpaena porcus).

The coralline community
In the rocky areas with little light in the Mediterranean there is an interesting community of chalky algae growing in adjacent horizontal plains to take advantage of the little light available. There are also large, colourful gorgonia.

In the Mediterranean, the so-called coralline area is characterised as colonised by a large number of chalky algae, among which other suspensive invertebrate organisms live: sponges, ascidia, briozou and sea fans, in a large variety of colours: yellows, pinks and oranges. The fall in the amount of light is one of the key factors for the development of these algae, which are enhanced while other disappear that need more light and which would undoubtedly annul them. Furthermore, the calcification gives them the necessary strength not to be eaten by certain herbivores. Although they grow very slowly, they fight to obtain as much light as possible, which causes a singular growth in horizontal plains, with even some layers covering and superimposing over others.

Other marine organisms frequently found in this community:
Flora: Lithophyllum expansum, Mesophyllum lichenoides, Plocamium cartilagineum.
Fauna: Ircinia oros, Petrosia ficiformis, red gorgonia (Paramuricea clavata), red precious coral (Corallium rubrum), european lobster (Homarus gamarus), Mediterranean locust lobster (Scyllarides latus), common brittle star (Ophiothrix fragilis), Astrospartus mediterraneus, Holoturia forskali, European conger (Conger conger), swallowtail sea perch (Anthias anthias), cardinal fish (Apogon imberbis), Leptogorgia sarmentosa, St. Peter’s fish (Zeus faber).

Inter-tidal zone community
Defying the hard conditions of the inter-tide area, characterised by the constant movement of the waves, there is a surprisingly large number of organisms.

The inter-tide area is characterised as the area under the influence of the tides, although in the Mediterranean they are not very large (20 cm at most). At certain times and for reasons of the movement of the sea (generally waves), these areas are momentarily left without water. The invertebrates that live here have adapted to this situation and are capable of keeping water in their bodies to survive until the sea returns. Furthermore, the fish are obliged to move periodically with the wave movement and the areas affected have a wealth of species where the stability of the water allows them.

Other marine organisms frequently found in this community:
Flora: Lithophyllum incrustans, Cystoseira mediterranea, Hypnea musciformis.
Fauna: Sycon raphanus, Sertularella ellisi, Mediterranean mussel (Mytilus galloprovincialis), acorn barnacle (Balanus perferatus), warty crab (Eriphia verrucosa), red sea anemone (Actinia equina), two-banded bream (Diplodus vulgaris), saddled bream (Oblada melanura).

The red coral community
This community is found in the cracks and entrances to caves and tunnels, where the light is sufficiently dampened for the algae component to be very small or nil. It is formed by large colonies of briozous, sponges, ascidia, hydraria and poliquets, and its development also depends on the food available. It is one of the most attractive sceneries of the sea beds.

Other marine organisms frequently found in this community:
Fauna: Red precious coral (Corallium rubrum), Spirastrella cunctatrix, Leptosammia cuvieri, Dendrophyllia ramea, yellow cluster anemone (Parazoanthus axinellae), Dendrodoris grandiflora, Protula tubularia, swallowtail sea perch (Anthias anthias), cuckoo-wrasse (Labrus bimaculatus), butterfly-blenny (Blennius ocellaris), cardinal fish (Apogon imberbes), longspine spinefish (Macroramphosus scolopax).

The Medes islands
The islas Medas are one of the most important reserves of marine flora and fauna in the western Mediterranean. This small archipelago is formed by seven small chalky islands and some reefs, with a total surface area of 21.5 hectares. It is located one mile offshore in front of Estartit beach.

The Islas Medas have been a protected area since 1990, and are the most important marine park in Catalonia. This marine reserve is an exceptional place for fish, for as human exploitation disappears, the number, variety and size of the species rapidly increase. However, a protected area suffers the problems derived from excessive diving.

Other marine organisms frequently found in this community:

Flora: Neptune Grass (Posidonia oceanica), Cystoseira mediterranea.
Fauna: Invertebrates: Hymeniacidon sanguinea, yellow sponge (Verongia aerophoba), Mediterranean mussel (Mytilus galloprovincialis).

Fish: wreckfish (Polyprion americanus), European conger (Conger conger), Trigger fish (Balistes carolinensis), scorpion fish (Scorpaena scrofa), dusky grouper (Epinephelus marginatus).

Birds: caspian gull (Larus cachinnans), cormorant (Phalacrocorax carbo), shag (Ph.aristotelis), little egret (Egretta garzetta), night heron (Nycticorax nycticorax), grey heron (Ardea cinerea).

Benthos life
Benthos, a Greek word that means “bottom”, refers to the community of organisms that live at the bottom of the marine floor – whether fixed to it, partially buried in it or moving around but never going very far from it.

From rocky to sandy beds and from well-lit waters to absolute obscurity, benthos is present in a wide diversity of environments, playing host to organisms that have adapted in surprising ways.

Barcelona Aquarium
The Barcelona Aquarium, located in the Old Port of Barcelona, is the main and only large aquarium in the city and in Catalonia. In addition, it is the most important center in the world on a Mediterranean theme. The complex was opened in 1995.

There are aquariums and exhibitions, as well as a cafeteria, shop, photo souvenir, auditorium and other services. The Aquarium has 35 different aquariums, 11,000 animals from 450 different species, an 80 meter underwater tunnel with more than 100 people working on it.

In 2015 it was visited by 1,549,480 visitors, ranking fourth among the most visited attractions in the city of Barcelona, only behind the Sagrada Familia, Park Güell and the FC Barcelona Museum.